The invention relates to a process and apparatus for distributing hydrocarbon feed to be contacted with catalyst. A field of the invention may be the field of fluid catalytic cracking (FCC).
FCC is a hydrocarbon conversion process accomplished by contacting hydrocarbons in a fluidized reaction zone with a catalyst composed of finely divided particulate material. The reaction in catalytic cracking, as opposed to hydrocracking, is carried out in the absence of substantial added hydrogen or the consumption of hydrogen. As the cracking reaction proceeds substantial amounts of highly carbonaceous material referred to as coke are deposited on the catalyst to provide coked or carbonized catalyst. This carbonized catalyst is often referred to as spent catalyst. However, this term may be misconstrued because the carbonized catalyst still has significant catalytic activity. Vaporous products are separated from carbonized catalyst in a reactor vessel. Carbonized catalyst may be subjected to stripping over an inert gas such as steam to strip entrained hydrocarbonaceous gases from the carbonized catalyst. A high temperature regeneration with oxygen within a regeneration zone operation burns coke from the carbonized catalyst which may have been stripped.
Although the carbonized catalyst carries coke deposits it may still have activity. U.S. Pat. No. 3,888,762 discloses mixing carbonized and regenerated catalyst for contact with the hydrocarbon feed. The regenerated catalyst may be in the range of 593° to 760° C. (1100° to 1400° F.) and the carbonized catalyst may be in the range of 482° to 621° C. (900° to 1150° F.). U.S. Pat. No. 5,597,537 discloses mixing the carbonized and regenerated catalyst in a blending vessel to allow the regenerated and carbonized catalyst to reach a temperature equilibrium before contacting the hydrocarbon feed. U.S. Pat. No. 7,935,314 B2 discloses baffles in the riser to obstruct upward catalyst flow to foster mixing. A mixed catalyst with more uniform temperature avoids undesirable hot spots that can generate nonselective cracking to reduce the value of the product hydrocarbons.
FCC can create a variety of products from heavier hydrocarbons. Often, a feed of heavier hydrocarbons, such as a vacuum gas oil, is provided to an FCC reactor. Various products may be produced, including a gasoline product and/or light olefins, such as at least one of propylene and ethylene. To produce more light olefins, product cuts from FCC effluent, such as naphtha, may be recycled to the riser reactor or to an additional riser reactor for additional catalytic cracking. These product cuts may be fed to the riser in a gaseous phase.
Current known methods of distributing a vapor stream to a riser are pose technical challenges. Typically, distribution would be accomplished by using a conventional feed distributor but due to the feed stream being in the vapor phase this would require a significant number of distributors to achieve sufficient mass distribution to the riser. Other known means of distributing the vapor stream, such as open pipes or pipes with slots at the end, are inefficient at evenly distributing the recycle stream in the riser.
It may be desirable to provide a distributor for distributing hydrocarbon feed to an FCC reactor.
It may be desirable to provide a distributor for distributing gaseous hydrocarbon feed to an FCC reactor.
It may also be desirable to provide a distributor for distributing hydrocarbon feed to an FCC reactor that assists with mixing of separate streams of catalyst.